1. Field of the Invention
This invention relates to a hydrostatic rotary drive suitable for use in construction equipment, such as excavators, with a pinion shaft that is rotationally mounted in a housing, a slewing pinion that is connected to the pinion shaft and an axial piston motor that uses the swashplate construction and has a rotating cylinder block with borings and pistons located in said borings.
2. Background Information
The slewing drives of the prior art for excavators generally consist of a high-speed axial piston power unit, a downstream one-stage or two-stage step-down gearing and a pinion shaft with a slewing pinion connected axially to it. A brake is also located between the axial piston power unit and the step-down gearing. Slewing drives of this type have been manufactured and sold since 1985 by Linde AG, Industrial Trucks and Hydraulics Division, Aschaffenburg.
The object of the invention is to make available a hydrostatic slewing drive of the type described above that has compact dimensions and is easy and economical to manufacture and install.
The invention includes a cylinder block that is integral, or in one piece, with the pinion shaft.
With the direct drive of the invention, there is no need for a step-down gearing, which requires a corresponding sizing of the axial piston motor for adequate flow passing. Further, in the invention, the pinion shaft bearing system assumes the function of the cylinder block bearing system. The cylinder block of the invention may have an extended bracket, as a result of which there is enough space available for a sufficiently large flow volume to be able to operate the axial piston motor as a low-speed engine (approximately 100 rpm). The invention achieves compact dimensions of the slewing drive and a significant reduction in the number of components, and thereby results in a drastic simplification of manufacture and assembly.
In one embodiment of the invention, the axial piston motor has a constant flow volume and the swashplate is formed on a housing component, which further minimizes the effort and expense of manufacture. The entire unit also takes up less space.
The admission and discharge of the hydraulic fluid to and from the borings of the cylinder block of the axial piston motor is very simple in one configuration of the invention. Specifically, the pistons may be supported by slippers on the swashplate. The swashplate may be provided with hydraulic fluid feed channels which can be connected to borings in the slippers and in the pistons. In this manner, no special control base receptacle is necessary, as is the case in the hydrostatic slewing drives of the prior art.
If the slewing pinion is detachably fastened to the pinion shaft/cylinder block, it can be replaced when it becomes worn. In this case, the pinion shaft/cylinder block can be reused.
The slewing drive of the invention may be provided with a brake that can be effectively connected with the pinion shaft/the cylinder block. The brake can straddle the cylinder block, for example. In one advantageous possible embodiment, the brake is located next to the swashplate base, and is connected in rotational synchronization with the pinion shaft/cylinder block by a torsion rod. As a result of this construction, it is not necessary to dismantle the axial piston motor to remove the brake. The torsion bar is a shaft that is subjected exclusively to torsion stress and can therefore be very slender. Further, when the brake is a wet, spring-loaded, multiple-disc brake, advantages are achieved with regard to the efficient utilization of space and increased efficiency.
The efficient utilization of space is further improved if there is at least one valve, in particular a control valve, between the swashplate and the swashplate base. The swashplate base is a plane perpendicular to the center axis, from which plane the swashplate projects axially toward the pinion shaft/the cylinder block.
In one configuration of the invention, the pinion shaft/the cylinder block is mounted in the housing by two helical bearings, in particular tapered roller bearings in an O-arrangement. This construction makes the absorption of large forces possible, including both internal power unit forces and external gearing forces.
A seal or sealing mechanism may be located between the pinion shaft/cylinder block and the housing in an area of the pinion shaft/cylinder block which is next to the slewing pinion. The seal or sealing mechanism can be replaced without having to remove the pinion shaft/cylinder block. This ability to replace the seal or sealing mechanism can be accomplished, for example, by using a detachable slewing pinion. If the slewing pinion is non-detachably connected with the pinion shaft/cylinder block, however, the seal or sealing mechanism may be in contact against a support and in the shape of an annular disc. Further, the seal or sealing mechanism and the support can be pushed over the slewing pinion.
Additional advantages and details of the invention are explained in greater detail below with reference to the exemplary embodiment illustrated in the accompanying schematic FIGURE wherein like reference numerals represent like elements throughout.